underwater defence

例句：

1. 1.The ship's underwater defence system is designed to protect it from enemy attack.
   该船的水下防御系统旨在保护它免受敌人攻击。
2. 2. The submarine's underwater defence was so effective that it could withstand a direct hit from a surface-to-air missile.
   潜艇的水下防御非常有效，以至于它可以抵御从水面到空中导弹的直接打击。
3. 3. The underwater defence system is crucial for the survival of marine life in the deep sea.
   水下防御系统对于海洋生物在深海的生存至关重要。